1. Field of the Invention
The present invention relates in general to apparatus for detecting the integrated value of current flow, apparatus for detecting the value of current flow and a battery pack employing those apparatus each of which serves to display the data relating to the battery energy remainder of a primary battery or a secondary battery/rechargeable battery for use in portable information terminals and the like, and more particularly to the circuit technology of making each of a apparatus for detecting the integrated value of current flow and a apparatus for detecting the value of current flow insensitive to the undesired offset of a detection circuits.
2. Description of the Related Art
In a portable information terminal which is typified by a note type personal computer, a user is very anxious about how much battery energy remainder the battery in use has and how long the battery in use can be used. Then, when the battery energy remainder has become equal to or lower than a predetermined value, it is required to take measures to warn a user of this fact and also to back up the data. For this purpose, there is required a method wherein the battery energy remainder of the battery can be aware of as precisely as possible.
Then, heretofore, the method has been proposed in which the charging/discharging current of the battery is monitored at all times to be integrated in order to display the data relating to the battery energy remainder. As for an example thereof, the method disclosed in JP-A-6-258410 is known. In JP-A-6-258410, there is shown the method wherein a resistor for detecting the current flow is inserted in series with a current part of a battery; the voltage which is developed across the resistor is amplified at a predetermined amplification factor; the voltage thus amplified is supplied as a control voltage to a voltage controlled oscillator; and as a result, a pulse oscillation signal having a frequency corresponding to the charging/discharging current value is obtained. In addition, there is also shown the method wherein by counting the number of pluses of the pulse oscillation signal, the integrated value of current flow is obtained.